This invention relates generally to a system for storing a quantity of continuous strip material such as tape or film. More particularly, the invention describes a method and apparatus for continuously storing motion picture film on edge on a flat rotating platter, as part of an endless loop film projection system.
It has long been recognized in motion picture projection that an endless loop system is desirable, in order to eliminate the need for manual rewinding and rethreading of film in repeated renditions of a program. A number of attempts have been made to provide for storing the film in a coil on a rotating turntable or platter in such a way as to minimize relative longitudinal movement between adjacent film layers in the coil, and yet permit, during each platter revolution, a predetermined length of film to be withdrawn from the center of the coil while the identical length of film is being added to the outside of the coil. The prior systems produce a series of singularly spaced, inwardly directed rounded cusps in the film coil, and are exemplified by the two U.S. Pat. Nos. 4,055,221 and 4,186,891 to Johnson, the U.S. Pat. No. 4,208,018 to Wilkerson, and the U.S. Pat. No. 4,504,025 to Potts. These patents in common with other prior systems include an application apparatus for incoming film which feeds or applies the incoming film to the rotating platter and means for shaping the film in the coil into a number of spaced inwardly directed cusps.
In another apparatus, the strip or film is transported from the edge of the platter toward the center of the coil by the tension of the strip in the outer layers. A cam is carried for rotation with the platter, with the cam having alternating arcuate sections and chord sections. The strip is applied to the outer periphery of the coil by a mechanism which includes a cam follower riding on the cam track as the platter rotates. This apparatus provides the desired cusps in the coil of film, but also involves an undesired tensioning of the film with a resultant rubbing of one layer of film against the adjacent layer.
A variation of the apparatus referred to in the preceding paragraph is shown in the copending application of Eddy U.S. Ser. No. 06/936,399, now Pat. No. 4,844,367 wherein a fixed roller is positioned at the arcuate outer periphery for urging the coil inward as the roller contacts the arcuate periphery of the coil.
Another apparatus is shown in the copending application of Eddy U.S. Ser. No. 07/068,325, now U.S. Pat. No. 4,836,463. In the apparatus of this copending application, the relationship of the application roller and the pusher roller is modified from that used in earlier units while the coil configuration is maintained essentially the same. The pusher roller is carried on the application arm so that it moves in and out with the in and out movement of the cam follower. In one embodiment, a four bar link is utilized to adjust movement of the pusher arm with reference to the application arm. Also, a servo arrangement provides a feedback type of operation for monitoring the amount of film being taken up on the platter as the platter rotates for automatically controlling the amount of film being wound onto the platter per revolution.
The two Eddy applications discussed above are assigned to the same assignee as is the present application.
Motion picture film has a tendency to curl in a transverse direction when a length of the film is in an unwound strip condition, as is the case when film is moving from the projector to the coil on the platter. Curling is a problem caused by the change in dimension of the emulsion side of the film with respect to the base side of the film and is exaggerated by changes in environmental conditions such as temperature and humidity.
While the apparatus referred to in the preceding paragraphs work satisfactorily in many installations, there are some situations, particularly high humidity environments, wherein problems in operation have been encountered. As a result, further improvements and changes in design and operation have been developed and are the subject of the present application.